1. Field of the Invention
The present invention relates generally to an image processing method and system for an X-ray apparatus for diagnosis of a circulatory organ, and more specifically to an image processing method and system for obtaining a road map as assisting means for guiding, in particular, a catheter to a target region in a subject.
2. Description of the Related Art
The road map image can be produced through the following image processing.
An operator inserts and advances a catheter to a target region in a blood vessel of a subject. While watching a fluoroscopic image displayed on a TV monitor, the operator advances the catheter into the blood vessel. In prior art devices, however, the blood vessel is not shown on the fluoroscopic image. Thus, it is difficult for the operator to decide in which direction the catheter should advance. To solve this problem, a contrast medium is often injected into the blood vessel from an end portion of the catheter, thus confirming the advancement of the catheter in the blood vessel.
Under the circumstances, a road map method is employed as an assisting method. In the road map method, an image of the blood vessel is superposed on the fluoroscopic image. More specifically, the contrast medium is injected into the blood vessel to obtain an image of the blood vessel through which the catheter will advance. Then, a mask image obtained before the contrast medium is injected is subtracted from a resulting contrast image. In a resulting subtraction image, a background (skeleton and/or muscle) is erased, and only an image of the blood vessel is displayed. Further, the image of the blood vessel is added to the fluoroscopic image. Namely, the image of the blood vessel and the fluoroscopic image are superposed on each other, thereby obtaining a road map image in which the blood vessel is shown on the fluoroscopic image. Consequently, the catheter can be easily advanced in a desired direction by referring to the road map image, and therefore the catheter can be easily operated.
The conventional road mapping, however, has the following problem.
Since the image of the blood vessel is superposed on the fluoroscopic image, that portion of the fluoroscopic image which corresponds to the blood vessel is not clearly seen. In particular, the direction of the tip portion of the catheter is very important when the catheter is operated in a branched region of the blood vessel. Thus, it is necessary that the image of the blood vessel be seen clearly. However, the image of the blood vessel, which is overlapped with the fluoroscopic image, becomes difficult to see.